Aromatic polyimides are known for their excellent thermal stability, chemical and solvent resistance, and light stability. They are used as industrial films, coatings, adhesives, and moldings. Economic fiber development from polyimide polymer has been hindered because of the insolubility of the imidized polymer in conventional solution-spinning solvents; fiber formation from melts has been hindered because the melt temperatures are very close to or higher than the polymer decomposition temperature.
Processing in the prior art has dealt with this problem by forming materials from the polyimide precursor, poly(amic acid). A typical method of manufacture consists of reaction of a dianhydride and a diamine to form a poly(amic acid). The latter is normally soluble and processable. After forming into a fiber or film, the poly(amic acid) is heat treated to imidize the carboxylic groups. This forms the completed insoluble polyimide.